I am thinking about building a XC hybrid... From scracth!

[Dustin_Drews]

Hello gents,
I am thinking about building my own hybrid quad with a CVT transmission to use for harescrambles and endurance races.
Basically from scratch... Have been reading on this section an have yet to see any other guys do the type of build I am thinking about...
This is what I am going for... A copy of the 250r frame geomerty with a no link rear shock.
The engine is going to be a built 400 Fugi engine, The same engine that is found in a 400 polaris scrambler that produces about 65 hp.
The tranny will be a CVT belt set up same used on most 4x4 quads.

What I am shooting for overall in my build is a quad that has a dry weight of 325 pounds. That I never have to change the oil or worry about cleaning the power valve it, or ever have to think about shifting in the tight woods meaning always being in the perfect gear but still has a top speed of around 80 mph.

Now I know that CVT transmissions have there place in the world they have been used for years on snowmobiles and they have pretty much taken over the Jr dragster seen, the UTV seen and they are even used in radio controlled cars!
I am wondering why people have not used them on 2 wheel drive sport race quads? The set up I am thinking is using a Fugi engine from a polarirs 400 scrambler.
Now being a 2 stroke it would be simple and being a 400 it should make good power and be pretty light. I could get 60hp really easy from what I have read?
I know the downside of the two strokes is the HIT of the powerband... But with the CV tranny you never feel it on a snowmobile so that should not be an issue on a quad and also eliminates the need for a powervalve.
Another benefit of of the cvt tranny and a 2 stroke engine is you completely eliminate all oil changes!
Because you have no engine or tranny to lube.
The down side that I can think of right now is free wheeling and no compression braking. With that being said everyone is switching to the recluse and loving it so this should not be an issue!
Another thought is you could have a rear had brake in place of the clutch for feathering the rear brake!
Fatigue is the big killer in these races and with out shifting and clutching I think it would take alot of strain off of the driver so he could focus on driving!
Also I think you would get more traction to the ground with the set up instead of dropping the clutch on a hill and spinning out?
I have not studied the engine upclose but I also think I could mount the engine flush with the bottom of the frame along with the radiator and maybe even lower the fuel tank some to get the lowest center of gravity possible!
With all the benefits I listed what are the down sides that I am overlooking?
Thanks for your time and input! Please do not hate me for trying to ruin your sport quads by putting a cvt in them.
Thanks for your time!
God Bless,
Dustin Drews

[250Renvy]

I think it's a cool idea. You could never do that to a stock 250R frame because it would be near impossible.

You would have to get some input from someone and design the frame around the motor. It would not be cheap, but you'd have a better product and it would fit without so many problems.

One of the problems you will have to investigate is 1. It's a polaris - their early quads were not well built. 2. Parts availability, ie how much of the scrambler 400 is still produced.

I have tested many projects to try to do something similar and find it is expensive and sometimes just doesn't work. For example - you will have to buy a 400 donor machine to analyze what parts you will need to donate to the new machine as well as what you can remove since it is a 4x4 quad.

I would like to do this same project with a Pilot 400 motor, but unfortunately the donor is crazy expensive and parts are in small supply.

I'm sure it won't matter but you also have to look at what classes you'll be able to run. It would seem open class would be the only option.

[Dustin_Drews]

The engine parts availability should not be an issue! Polaris never built there own engine it was built by fugi or subaru I beleve you can still get the engine from them!
You are correct about it being expensive but I should have mentioned that I am a fabricator myself with the tooling to accomplish the build myself!
Do you know how Big the scrambler engine is? with no tranny I was thinking it would be pretty small? Just the jackshaft CVT system may be rather large that they mounted to it!
So besides cost is there any other down sides I am overseeing? If this works out I may look into building them as a hobby and selling them!
I do not know what rules are in effect about classes but if I am a manufacturing them I should be able to drive them in any class I want!
Thanks for the info!
God Bless,
Dustin
I forgot to mention that the scrambler was built as a 2 wheel drive model with out the 4x4 gear box! So this should help fitment!

[C41Xracer]

cant wait to see this build

[audioworks04]

Its a great idea, just hasnt been done due to the weight/size of the motor. These are going to be your biggest problems to overcome. The polaris 400 does make great power, but as an overall machine it was really tall and heavy. If you can figure out how to overcome these then you will be set. A typical 250r will not work like 250renvy stated, you will need a wider frame with more head room.

[C41Xracer]

why are you guys thinking about the scrambler 400 only? Polaris made a sport 400 also, 2wd only. The engine isnt all that big, yeah it is wide but i think it could be done and not be all that expensive

[Dustin_Drews]

The sport was 2 wheel drive... I just need to find one and do some looking to ensure that I can get everything to fit in a nice clean package!
God Bless,
Dustin